Editing Perspiration (section)

==Mechanism==
[[File:Sweaty runner.jpg|thumb|alt=A young man competing in the 2014 Carlsbad Triathlon jogs on a paved path along a beach in Southern California. His expression shows the labor of his effort.|The evaporation of sweat on the skin cools the body.]]
Sweating allows the body to regulate its temperature. Sweating is controlled from a center in the preoptic and anterior regions of the brain's [[hypothalamus]], where thermosensitive neurons are located. The heat-regulatory function of the hypothalamus is also affected by inputs from temperature receptors in the [[skin]]. High skin temperature reduces the hypothalamic set point for sweating and increases the [[Gain (electronics)|gain]] of the hypothalamic [[feedback]] system in response to variations in core [[temperature]]. Overall, however, the sweating response to a rise in hypothalamic ('core') temperature is much larger than the response to the same increase in average skin temperature.{{citation needed|date=July 2022}}

Sweating causes a decrease in core temperature through evaporative cooling at the skin surface. As high energy molecules evaporate from the skin, releasing energy absorbed from the body, the skin and superficial vessels decrease in temperature. Cooled venous blood then returns to the body's core and counteracts rising core temperatures.{{citation needed|date=March 2024}}

There are two situations in which the nerves will stimulate the sweat glands, causing perspiration: during physical heat and during emotional stress. In general, emotionally induced sweating is restricted to [[Hand#Areas|palm]]s, [[Sole (foot)|sole]]s, [[armpit]]s, and sometimes the [[forehead]], while physical heat-induced sweating occurs throughout the body.<ref>{{Cite journal |last=Kameia |first=Tomoya |last2=Tsudab |first2=Takao |last3=Kitagawab |first3=Shinya |last4=Naitoha |first4=Ken |last5=Nakashimaa |first5=Koji |last6=Ohhashi |first6=Toshio |date=1998-06-05 |title=Physical stimuli and emotional stress-induced sweat secretions in the human palm and forehead |journal=[[Analytica Chimica Acta]] |volume=365 |issue=1–3 |pages=319–326 |bibcode=1998AcAC..365..319K |doi=10.1016/S0003-2670(97)00642-9 |issn=0003-2670 |eissn=1873-4324 |oclc=01716731 |df=dmy-all}}</ref>

People have an average of two to four million sweat glands, but how much sweat is released by each gland is determined by many factors, including sex, genetics, environmental conditions, age and fitness level. Two of the major contributors to sweat rate are an individual's fitness level and weight. If an individual weighs more, sweat rate is likely to increase because the body must exert more energy to function and there is more body mass to cool down.  On the other hand, a fit person will start sweating earlier and more readily. As someone becomes fit, the body becomes more efficient at regulating the body's temperature and sweat glands adapt along with the body's other systems.<ref>{{Cite web |last=Hansen |first=Julieann |date=2013-05-22 |title=The Science of Sweat |url=http://certification.acsm.org/blog/2013/may/the-science-of-sweat |archive-url=https://web.archive.org/web/20130921055518/http://certification.acsm.org/blog/2013/may/the-science-of-sweat |archive-date=2013-09-21 |access-date=2023-01-13 |website=[[American College of Sports Medicine]] |df=dmy-all}}</ref>

Human sweat is not pure [[water]]; though it contains no protein, it always contains a small amount (0.2–1%) of [[solute]]. When a person moves from a [[cold]] [[climate]] to a [[Temperature|hot]] climate, adaptive changes occur in the sweating mechanisms of the person. This process is referred to as [[acclimatization]]: the maximum rate of sweating increases and its solute composition decreases. The volume of water lost in sweat daily is highly variable, ranging from {{convert|100|to|8,000|mL/day}}. The solute loss can be as much as 350{{nbsp}}mmol/d (or 90{{nbsp}}mmol/d acclimatised) of [[sodium]] under the most extreme conditions. During average intensity exercise, sweat losses can average up to {{convert|2|litres}} of water/hour.  In a cool climate and in the absence of [[exercise]], sodium loss can be very low (less than 5&nbsp;mmol/d). Sodium concentration in sweat is 30–65&nbsp;mmol/L, depending on the degree of acclimatisation.{{citation needed|date=March 2024}}

Horses have a thick, waterproofed, hairy coat that would normally block the rapid translocation of sweat water from the skin to the surface of the hair required for evaporative cooling. To solve this, horses have evolved a detergent-like protein, [[BPIFA4P|latherin]], that they release at high concentrations in their sweat.<ref name=":2" />  Their perspiration unlike humans is created by apocrine glands.<ref name="McCutcheon Geor3" /> This protein, by wetting the horses' coat hairs facilitate water flow for cooling evaporation. The presence of this protein can be seen in the lathering that often occurs on the coats of sweating horses, especially when rubbed.<ref name=":2" /> In hot conditions, horses during three hours of moderate-intensity exercise can lose {{convert|30|to|35|L}} of water and {{convert|100|g}} of sodium, {{convert|198|g}} of chloride and {{convert|45|g}} of potassium.<ref name="McCutcheon Geor3" />